False twisting device

ABSTRACT

The invention is related to a false twister for the production of synthetic textured or stretch-type yarns or filaments, consisting of two or more successive internal friction twisters, wherein the inlet-end friction surfaces of the internal friction twister mouthpieces have a high coefficient of friction whilst the friction surfaces of the outlet mouthpieces have a low coefficient of friction in relation to the friction surfaces at the inlet end.

I United States Patent 1 1 1111 3,879,927

Bueb et al. Apr. 29, 1975 FALSE TWlSTlNG DEVICE 3.535.866 10/1970Tsuruta et al 57/774 x 3,537,250 ll/l970 Mackintosh 57/774 [751 lnvcmmsOPlddenr Karma: 3,670,488 6/1972 Richter 57/774 "8" Smbergl Edgar5.740.939 5/1973 Nevcuk.... 57/7745 Muschelknautz, usen; 3,745,7557/1973 Kcto 57/77 4 Wolfgang Rellensmann, Zons u. Neuss, all of GermanyPrimarv Examiner-Donald E. Watkins 73 A B Akt ll h ft, i 1 sslgnee zzg rg g i Arlorney, Agent, or Frrm-Plumley & Tyner [22] Filed: Mar. 20, I974[21] Appl. No.; 452,928 ABSTRACT pp Priority Data The invention isrelated to a false twister for the pro- Mar. 20. 1973 Germany 23l3723duction of synthetic textured or stretch-type yarns or filaments,consisting of two or more successive inter- [52] U.S. Cl 57/77.4; 57/156nal friction twisters, wherein the inlet-end friction sur- [5] Int. Cl.D02g l/04 faces of the internal friction twister mouthpieces have [58]Field of Search 57/77.3-77.45, a high coefficient of friction whilst thefriction sur- 57/156 faces of the outlet mouthpieces have a lowcoefficient of friction in relation to the friction surfaces at the [56]References Cited inlet end.

UNITED STATES PATENTS 3.066.473 lit/1962 Mucdu 57/774 8 Claims, 7Drawing Figures PMENIEBAPRZSISYS 3,879,927

sum 1 of 3 FIG. I

FALSE TWISTING DEVICE This invention relates to a process and a falsetwister for the production of textured and/or stretch-type textilefilaments or yarns.

In the so-called torsion process for texturing yarns or filamentsconsisting at least partly of thermoplastic material, the yarns orfilaments are passed in twisted form through a heating zone and acooling zone. The yarns or filaments are twisted for example by means ofa false twister which follows the heating and cooling zone in thedirection of travel of the yarn or filament, and which transmits to thefilament a frictional force producing a torsional moment in thefilament. Heating and subsequent cooling of the filament in its twistedform fixes a state of permanent deformation in the filament which isresponsible for the characteristic properties of the filaments thusproduced. In order to produce a filament of high quality, it isnecessary on the one hand that the twister should produce a certaintorsional moment governed for example by the material. denier and numberof the individual capillaries and by quality features of the endproduct. On the other hand, the tension to which the filament issubjected as it passes through the twister should not be excessivelyincreased so that the deformation fixed into the filament in the fixingzone is not eliminated or destroyed.

It is known that there are various technical possibilities for bringinga travelling filament into contact with friction surfaces of a twisterto produce a torsional moment in the filament. For example, British Pat.No. 797.051 describes an arrangement in which the filament is drawnthrough a twist tube whose internal surfaces, which come into frictioncontact with the filament. consist of a material having a high frictioncoeffcient. in one preferred embodiment of this so-called internalfriction twister for example. a mouthpiece consisting of a materialhaving a high friction coefficient is fitted both to the inlet end andto the outlet end of the twist tube (in the direction of travel of thefilament). German Offenlegungsschrift No. 2.123.618 describes afriction-type texturing arrangement comprising at least two twist tubesthrough which the filament is guided in such a way that a looping angleof at least about 360 is obtained, and which is distinguished by thefact that the friction inserts consist of a ceramic or a hard metal.

However, it has been found that. in the event of an increase in the rateof filament travel in internal friction twisters of this kind, not onlyis the torsional moment transmitted to the filament altered, the ratiobetween the tension prevailing in the filament on leaving the twisterand the tension which had prevailed in the filament before entry intothe twister is also increased. In view of this effect. a certain ratiohas to be maintained between the rotational speed of the twister or thespeed of the friction surfaces and the rate of filament travel to ensurethat the tension prevailing in the filament on leaving the twister doesnot become excessive. If the filament tension ratio which is favourableto the particular filament and which. in general. is preferably low, isto be maintained. the rotational speed of the twister has to beincreased accordingly. However. it is not possible in practice toincrease the rotational speed of the twister arbitrarily because.technically, this becomes increasingly more difficult beyond certainrotational speeds. for example from the point of view of the servicelife of the ball bearings. controlling the centrifugal forces generatedat the mouthpieces or avoiding a high noise level.

Accordingly. it is desirable to have a twister which transmits asufficiently high torsional moment to the filament and, at the sametime. produces little or no increase in filament tension, especially athigh rates of filament travel and, in relative terms. low rotationalspeeds of the twister.

lnventions have been developed with a view to transmitting a torsionalmoment to the filament on the one hand and to accelerate rather thandecelerate the filament as it passes through the twister on the otherhand. German Offenlegungsschrift No. 2,040,749 describes a frictiontwister which consists of three externally mounted rings which areinclined relative to the direction of filament travel and along whoseintern a] friction surfaces the filament travels. in addition, GermanOffenlegungsschrift No. 2,038,067 for example describes an arrangementin which the filament is guided over a specially shaped friction surfaceinto a rotating twist box and. after changing direction over a guideroller. leaves the twister again through the inlet opening. Twisterswhich are designed to produce the favourable properties referred toabove in this or a similar manner. are generally complicated. whichapplies in particular to those comprising several rotating componentsand shafts, or are unsatisfactory for example in regard to generation ofthe torsional moment.

The object of the present invention is to provide a twister whichfunctions on the technically simple principle of internal frictiontwisting and which, in addition to generating a satisfactory torsionalmoment, guarantees a sufficiently low filament tension ratio, especiallyin cases where there is a low ratio between the rotational speed of thetwister and the rate of filament travel.

According to the invention, there is provided a false twister for theproduction of synthetic textured or stretch-type yarns or filaments,consisting of two or more successive internal friction twisters. whereinthe inlet-end friction surfaces of the internal friction twistermouthpieces l have a high coefficient of friction whilst the frictionsurfaces of the outlet mouthpieces 2 have a low coefficient of frictionin relation to the friction surfaces at the inlet end.

According to the invention there is also provided a process for thesimultaneous stretching and texturin g of synthetic filaments or yarnsusing internal friction twisters. wherein the filament or yarn, afterpassing through a heating and a cooling zone. in which it is alsostretched. is guided through two or more internal friction twisters anda high torsional moment in relation to the negligibly low torsionalmoment applied at the outlet end is imparted to the filament or yarn bythe inletend friction surfaces of the twister mouthpieces.

The friction coefficient of the friction surfaces at the inlet endshould preferably be between 0.4 and 0.7. depending upon the material tobe textured. Friction coefficients at the inlet end between 0.5 and 0.6have proved to be particularly favourable. The friction coefficient ofthe mouthpieces at the outlet end should be as low as possible.preferably less than 0.3.

In a simple internal friction twist tube. as shown in FIG. 1. an inletend mouthpiece l and an outlet end mouthpiece 2 are arranged in a twisttube 3 which is driven, for example. by means of a drive belt 4. Thefilament 5 is drawn through the twist tube in the manner illustrated inFIG. I. A torsional moment is generated in the filament through itsfrictional contact with the rotating mouthpieces 1 and 2. The inlet endand outlet end looping angles (b1 and 422 may be between 45 and 90, forexample, according to requirements. It has been found that the ratiobetween the tension prevailing in the filament on leaving the twist tubeand the tension which had prevailed in the filament before entry intothe twist tube is substantially reduced if the mouthpiece 2 at theoutlet end has a lower coefficient of friction than the mouthpiece l atthe inlet end. Unfortunately, the torsional moment transmitted from thetwist tube to the filament also decreases with a mouthpiece combinationsuch as this. However, if after leaving the twist tube the filament isguided through a second twist tube similarly equipped with differentmouthpieces, it is surprisingly found that, on the one hand, there isstill a low ratio between the filament tensions after and before thisdouble twister whilst, on the other hand, a sufficiently high torsionalmoment is generated.

In one embodiment of a twister according to the invention as illustratedin FIG. 2, the filament 5 initially passes over an inlet mouthpiece 1having a high coefficient of friction and then over an outlet mouthpiece2 having as low a friction coefficient as possible (for example polishedsteel or ceramic). In the embodiment illustrated in FIG. 2 with twosuccessive twist tubes, the filament again passes over a second inletmouthpiece I having a high coefficient of friction and over a secondoutlet mouthpiece 2 having as low a coefficient of friction as possible.The outlet mouthpieces 2 can be regarded as substantially frictionlessguides by which the twisted filament is brought from a preceding into afollowing twist tube.

Naturally the invention also includes filament guides in which thefilament is guided twice through the same twist tube. In an arrangementof, for example, two twist tubes of the kind shown in FIG. 2a, thefilament first of all passes through the first twist tube, then throughthe second twist tube and finally back through the first twist tube, incases where this procedure is adopted.

Instead of being guided over a smooth outlet mouthpiece, the filamentcan also be guided over a filament guide, preferably in the form of aroller 6, at the outlet end of the twist tube, as shown in FIGS. 3, 4and 4a, in order to avoid contact between the filament and the twisttube at the outlet end. In order to enhance the filament-transportingeffect of the mouthpiece at the inlet end, the guide roller 6 isarranged in such a way, in a preferred embodiment illustrated in FIGS. 4and 40, that the filament is only slightly deflected from its path, asseen in a vertical projection on to the inlet mouthpiece. The distance damounts to about (0.2 0.8) R,. The distance e is derived from the needfor the filament to be guided close to, but without touching, the outletedge of the twist tube.

Accordingly, another preferred embodiment of the invention is a falsetwister consisting of two or more successive internal friction twisters,distinguished by the fact that the internal friction twister mouthpieces2 are missing from the outlet end and are replaced by filament guideelements known per se, preferably in the form of rollers.

In order to enhance the filament-transporting effect of a twister ofthis kind which is only effective at the inlet end, it is possibleaccording to another aspect of the invention to increase the size of themouthpieces to such an extent that an optimum ratio exists betweentorque generation, filament tension ratio and the uniformity with whichthe frictional force is transmitted.

In a conventional mouthpiece, the characteristic radii R,- and R are,for example, between 10 and 15 mm and between 20 and 30 mm,respectively, whereas with an enlarged mouthpiece they may be, forexample, between 20 and 30 mm and between 40 and mm, respectively. Theradius of curvature r may be, for example, between 5 and 10 mm. Thesignificance of the radii R,, R, and r can be seen from FIGS. 4 and 4a.The advantage of increasing the geometry of the mouthpiece is that thesurface speeds are increased by the increase factor. It has alsosurprisingly been found in practice that, by increasing the size of themouthpieces, it is also possible to enhance the transporting effect ofthe inlet mouthpiece.

Accordingly, the invention also relates to a false twister consisting oftwo or more successive internal friction twisters acting at the inletend, distinguished by the fact that the radii R, and R amount to between20 and 30 mm and to between 40 and 60 mm, respectively.

The advantages afforded by the invention are in par ticular the factthat, by arranging one behind the other, two or more internal frictiontwist tubes whose inlet and outlet friction surfaces have been modifiedin re gard to their friction coefficient in accordance with theinvention, it is possible to obtain a twister which, whilst producingthe same torsional moment, has a lower filament tension ratio than aconventional internal friction twist tube with two mouthpieces havingthe same coefficients of friction.

By means of the specific arrangement of modified twist tubes one afterthe other, torsional moment and filament tension ratio can be adaptedwithin wide limits to meet the requirements of a particular filament andprocess, in particular, by the use of a modular system.

The invention is described in more detail in the following withreference to the accompanying drawings, wherein:

FIG. I shows a conventional internal friction twist tube with twoidentical mouthpieces.

FIG. 2 shows one embodiment of a false twister according to theinvention.

FIG. 2a shows a second embodiment of the false twister according to theinvention.

FIG. 3 shows a third embodiment of the false twister according to theinvention.

FIG. 4 shows the path followed by the filament through a twist tube inaccordance with the invention having staggered outlet rollers.

FIG. 5 illustrates a texturing process using a false twister accordingto the invention (simultaneous stretching and texturing).

According to FIG. 5, a filament coming from a bobbin 7 travels throughdelivery rollers 8 and passes over a heater 9. The filament then travelsthrough two successive internal friction twisters I0 and 11, iscontinuously stretched by the stretching godet l2 and 1S wound into apackage by means of the winding unit 13, optionally after passingthrough a second heatlng zone and following the application of apreparation.

The invention also relates to a process for the slmultaneous stretchingand texturing of synthetic filaments and yarns using internal frictiontwisters and a heatfixing zone, distinguished by the fact that. afterpassing through the heat-fixing zone, in which it is also stretched, thefilament or yarn is guided through two or more internal frictiontwisters, and a high torsional moment in relation to the negligibly lowtorsional moment applied at the outlet end is imparted to the filamentor yarn by the inlet end friction surfaces of the twister mouthpieces.

The process is suitable for texturing yarns consisting at least partlyof thermoplastic material. It is preferred to use yarns of polyamides,such as polyamide-6 and polyamide-6,6, or yarns of polyesters, such aspolyethylene terephthalate.

The following Example is to further illustrate the invention withoutlimiting it.

EXAMPLE A polyamide yarn (polyamide-6 of dtex 22/3) is stretched bystretching rollers in a ratio of l 3.3 and is introduced at atemperature of [65C through a heated zone into the false twisteraccording to the invention illustrated in FIG. 4 at a rate of 700 metresper minute. The twist tube is rotated at 18,000 rpm. The mouthpieceshave an internal radius of mm and an external radius of 45 mm. The inletmouthpieces are made of Vulkollan 70 Shore, and the outlet mouthpiecesof polished steel. The textured filament thus produced has a coldwatershrinkage of 30 to 50 percent. If a yarn of the same quality were to betwisted with a simple, conventional twist tube equipped with two normalVulkollan mouthpieces, the twist tube would have to rotate at around25,000 r.p.m.. Thus, by using the twister according to the invention,the rotational speed of the twist tubes can be reduced by 28.6 percent,which is desirable from the operational point of view.

We claim:

1. A false twister for the production of synthetic textured orstretch-type yarns or filaments, consisting of two or more successiveinternal friction twisters, wherein the inlet-end friction surfaces ofthe internal friction twister mouthpieces (l have a high coefficient offriction whilst the friction surfaces of the outlet mouthpieces (2) havea low coefficient of friction in relation to the friction surfaces atthe inlet end.

2. A false twister as claimed in claim I, wherein the inlet-end frictionsurfaces of the internal friction twister mouthpieces have a frictioncoefficient of 0.4 to 0.7.

3. A false twister as claimed in claim 2, wherein the inlet-end frictionsurfaces of the internal friction twister mouthpieces have a frictioncoefficient of 0.5 to 0.6.

4. A false twister as claimed in claim 1, wherein the frictioncoefficient of the mouthpiece at the outlet end is less than 0.3.

5. A false twister as claimed in claim 1, wherein the internal frictiontwister mouthpieces (2) are missing at the outlet end and are replacedin their function as filament guides by filament guide elements knownper se.

6. A false twister as claimed in claim 5, wherein a roller (6) is usedas the filament guide element.

7. A false twister as claimed in claim 1, wherein the radii R, and R, ofthe twister mouthpieces amount to between 20 and 30 mm and to between 40and 60 mm, respectively.

8. A process for the simultaneous stretching and texturing of syntheticfilaments or yarns using internal friction twisters, wherein thefilament or yarn, after passing through a heating and a cooling zone, inwhich it is also stretched, is guided through two or more internalfriction twisters and a high torsional moment in relation to thenegligibly low torsional moment applied at the outlet end is imparted tothe filament or yarn by the inletend friction surfaces of the twistermouthpieces.

1. A false twister for the production of synthetic textured orstretch-type yarns or filaments, consisting of two or more successiveinternal friction twisters, wherein the inlet-end friction surfaces ofthe internal friction twister mouthpieces (1) have a high coefficient offriction whilst the friction surfaces of the outlet mouthpieces (2) havea low coefficient of friction in relation to the friction surfaces atthe inlet end.
 2. A false twister as claimed in claim 1, wherein theinlet-end friction surfaces of the internal friction twister mouthpieceshave a friction coefficient of 0.4 to 0.7.
 3. A false twister as claimedin claim 2, wherein the inlet-end friction surfaces of the internalfriction twister mouthpieces have a friction coefficient of 0.5 to 0.6.4. A false twister as claimed in claim 1, wherein the frictioncoefficient of the mouthpiece at the outlet end is less than 0.3.
 5. Afalse twister as claimed in claim 1, wherein the internal frictiontwister mouthpieces (2) are missing at the outlet end and are replacedin their function as filament guides by filament guide elements knownper se.
 6. A false twister as claimed in claim 5, wherein a roller (6)is used as the filament guide element.
 7. A false twister as claimed inclaim 1, wherein the radii Ri and Ra of the twister mouthpieces amountto between 20 and 30 mm and to between 40 and 60 mm, respectively.
 8. Aprocess for the simultaneous stretching and texturing of syntheticfilaments or yarns using internal friction twisters, wherein thefilament or yarn, after passing through a heating and a cooling zone, inwhich it is also stretched, is guided through two or more internalfriction twisters and a high torsional moment in relation to thenegligibly low torsional moment applied at the outlet end is imparted tothe filament or yarn by the inlet-end friction surfaces of the twistermouthpieces.